Fixup deprecated copy warning for clang 10+ in MultiIndex (#16291)
Fixup deprecated copy warning for clang 10+ in MultiIndex (#16291)

jessecarterMOOSE/moose,milljm/moose,idaholab/moose,SudiptaBiswas/moose,SudiptaBiswas/moose,bwspenc/moose,bwspenc/moose,idaholab/moose,nuclear-wizard/moose,andrsd/moose,lindsayad/moose,lindsayad/moose,dschwen/moose,nuclear-wizard/moose,lindsayad/moose,laagesen/moose,andrsd/moose,SudiptaBiswas/moose,sapitts/moose,bwspenc/moose,lindsayad/moose,jessecarterMOOSE/moose,sapitts/moose,dschwen/moose,milljm/moose,idaholab/moose,harterj/moose,dschwen/moose,nuclear-wizard/moose,bwspenc/moose,laagesen/moose,sapitts/moose,laagesen/moose,SudiptaBiswas/moose,dschwen/moose,idaholab/moose,harterj/moose,harterj/moose,lindsayad/moose,harterj/moose,sapitts/moose,sapitts/moose,bwspenc/moose,milljm/moose,andrsd/moose,harterj/moose,jessecarterMOOSE/moose,laagesen/moose,andrsd/moose,idaholab/moose,laagesen/moose,milljm/moose,nuclear-wizard/moose,andrsd/moose,milljm/moose,dschwen/moose,jessecarterMOOSE/moose,SudiptaBiswas/moose,jessecarterMOOSE/moose